The present invention generally relates to the sensing of air leaks in tires and tire manufacturing machines, and more specifically to the sensing of small air leaks in a tire mounted on a tire uniformity machine and the leakage of air from the tire uniformity machine.
In the art of manufacturing pneumatic tires, rubber flow in the tire mold or minor differences in the dimensions of the belts, beads, liners, treads, plies of rubberized cords, etc., sometimes cause non-uniformities in the final tire. Non-uniformities of sufficient amplitude will cause force variations on a surface, such as a road, against which the tires roll producing vibration and noise. When such variations exceed an acceptable maximum level, the ride and handling of a vehicle utilizing such tires will be adversely affected.
Tire uniformity machines are used to monitor the quality of the tire production process and may guide or incorporate corrective measures such as the grinding to improve the balance and uniformity of a tire. In general, a tire uniformity machine (TUM) subjects a tire to normal conditions of mounting, pressurization, rotation and load while collecting measurement data on variations of deflection, force and velocity. A tire uniformity machine typically includes an assembly for rotating a tire against the surface of a rotating loading wheel. In tis testing arrangement, the loading wheel is moved in a manner dependent on the forces exerted by the rotating tire and those forces are measured by appropriately placed measuring devices. When a tire being tested yields less than acceptable results, shoulder and/or center rib grinders can be used to remove a small amount of the tire tread at precisely the location of the non-uniformities detected by the measuring devices. In a sophisticated tire uniformity machine, the measurements are stored and interpreted in digital form by a computer and rubber is removed from the tire tread using grinders controlled by the computer. Examples of machines utilizing these methods are disclosed in U.S. Pat. Nos. 3,739,533; 3,946,527; 4,914,869 and 5,263,284.
The TUM as well as other tire testing and manufacturing machines require that a tire be mounted and quickly inflated to a desired pressure. For example, with a TUM, the tire being tested is mounted and inflated to the desired pressure, typically about 30 pounds per square inch (psi) in about 1 to 2 seconds. The speed of inflation is an important factor since the tests are being conducted on the factory floor. Unavoidably, the tires themselves sometimes have small even microscopic air leaks. In other cases the TUM""s or other tire manufacturing machines can themselves have small air leaks in the inflation circuits. Since the TUMs and other such testing and manufacture machines are connected to a high pressure air source, the air leakage, microscopic sized holes in the tire and/or the air leaks in the in the inflation circuit of the machines are not recognized.
Since both recognition of flaws in tires before sending them to a customer and elimination of defects of the tire uniformity machine are important to save money, there is a need for improved methods to monitor air leakage during the uniformity measurement of a tire mounted on a TUM or other tire testing and manufacturing machines. Moreover, it is also important to detect air leaks in the in the inflation circuit of the machines for reasons of economy.
The present invention relates to a method for detecting air leaks in tires and in a tire testing machine. The method includes mounting each of the tires on the tire testing machine; inflating each or the tires with an air flow from an inflation system to a first pressure; maintaining each of the tires at the first pressure by continued supply of air from the inflation system into the tire; measuring the flow of the continued supply of air with a calorimetric flow sensor calibrated to output a sensor signal having a full scale value corresponding to an identical model tire mounted on the tire testing machine with no air leaks in the model tire or the testing machine; comparing the flow of the continued supply of air with an averaged flow for previously measured tires mounted on the tire testing machine with no air leaks in the tires or the testing machine; and outputting a control signal indicating an air leak if the sensor signal is 20% to 100% of the full scale value.
The method includes calibrating the calorimetric flow sensor so that 50% of the full scale value corresponds to a pre-selected sized hole in the model tire, less than 50% is an indication of a smaller hole than the pre-selected hole in the model tire and more than 50% is an indication of a larger hole than the pre-selected hole in the model tire.
The method of measuring the flow of the continued supply of air with a calorimetric flow sensor includes the step of measuring the caloric depletion from the continued supply of air maintaining the tire at the first pressure.
The method also includes generating an alarm signal signaling to check for sensor failure if the sensor signal is at full scale value for a predetermined number of tires mounted onto the testing machine.
The method further includes stopping the tire testing machine, marking the tire and/or sending the tire down a scrap conveyor whenever the sensor signal is 20% to 100% of the full scale value.
The method further includes inflating each of the tires with an air flow from an inflation system to a second pressure to set tire beads of the fire on machine rims of the testing machine; and deflating each of the tires to the first pressure corresponding to a rated pressure of the tire.
The method includes loading each of the tires by a load wheel of the tire testing machine; and subjecting each of the tires to normal conditions of mounting, inflation, load and rotational speed while measuring and collecting tire uniformity measurement data;
The method includes setting a pressure control signal with a computer corresponding to the first pressure to which the tire will be inflated; directing the pressure control signal through a signal line to a pneumatic servo valve; controlling a pneumatic air booster disposed in an air line carrying the air flow to each of the tires with the pneumatic servo valve so that the air flow through the pneumatic air booster is controlled in order that the pressure in the tire is at the first pressure set by the computer.
The method of measuring the flow of the continued supply of air includes the measurement of an air flow of less than 1 SCFM; and inflating the tire with an air flow from the inflation system to a second pressure with an air flow of up to 1200 SCFM.
The system of the present invention relates to a system for detecting air leaks in tires and in a tire testing machine. The system includes means for mounting each of the tires on the tire testing machine; means for inflating each of the tires with an air flow from an inflation system to a first pressure; means for maintaining each of the tires at the first pressure by continued supply of air from the inflation system into the tire; means for measuring the flow of the continued supply of air with a calorimetric flow sensor calibrated to output a sensor signal having a full scale value corresponding to an identical model tire mounted on the tire testing machine with no air leaks in the model tire or the testing machine; means for comparing the flow of the continued supply of air with an averaged flow for previously measured tires mounted on the tire testing machine with no air leaks in the tires or the testing machine; and means for outputting a control signal indicating an air leak if the sensor signal is 20% to 100% of the full scale value.
The system further includes means for calibrating the calorimetric flow sensor so that 50% of the full scale value corresponds to a pre-selected sized hole in the model tire, less than 50% is an indication of a smaller hole than the pre-selected hole in the model tire and more than 50% is an indication of a larger hole than the pre-selected hole in the model tire.
The system further includes means for generating an alarm signal signaling to check for sensor failure if the sensor signal is at its minimum value for a predetermined number of tires mounted onto the testing machine.
The system further includes means for stopping the tire testing machine, marking the tire and/or sending the tire down a scrap conveyor whenever the sensor signal is 20% to 100% of the full scale value.
The system also includes means for inflating each of the tires with an air flow from an inflation system to a second pressure to set tire beads of the tire on machine rims of the testing machine; and means for deflating each of the tires to the first pressure corresponding to a rated pressure of the tire.
The system also includes means for setting a pressure control signal with a computer corresponding to the first pressure to which the tire will be inflated; means for directing the pressure control signal through a signal line to a pneumatic servo valve; and means for controlling a pneumatic air booster disposed in an air line carrying the air flow to each of the tires with the pneumatic servo valve so that the air flow through the pneumatic air booster is controlled in order that the pressure in the tire is at the first pressure set by the computer.
The system including means for measuring the caloric depletion from the continued supply of air maintaining the tire at the first pressure, means for measuring the flow of the continued supply of air includes means for measuring an air flow of less than 1 SCFM and means for inflating the tire with an air flow from the inflation system to a second pressure with an air flow of up to 1200 SCFM.